Various instruments have been utilized for detecting viscoelastic properties of fluid, including adhesion, cohesion, surface tension, viscosity, and yield stress. One of the major difficulties encountered in the measurement of viscoelastic properties of fluid, other than “ideal” or Newtonian fluids, are the properties being measured may be fluctuating during measurement. For instance, it has been found that female saliva samples from the oral cavity undergo distinct in-phase physiochemical changes during the menstrual cycle.
FIG. 1 is a graph illustrating a relationship of the viscoelasticity of female sublingual saliva to blood hormones over a fourteen day period. It is known that the cervical mucus of a female has a minimum thinness or highest fluidity just before ovulation and closely coincident with the surge in estradiol and in the luteinizing hormone (LH) peak—a phenomenon that led to the development of techniques for monitoring the viscoelasticity and other properties of cervical mucus as a predictor of time of ovulation, and the improvements in rheometer or viscometer apparatus for measuring such viscoelastic properties. Though the viscoelasticity of the cervical mucus has several small dips in its characteristic curve of viscosity versus time preceding, during and following ovulation (a four-day period), there is a distinct identifiable minimum coincident with the peaking of estradiol, representing the thinning of bodily secretions. During the immediate pre-ovulatory phase, for a period of four to five days under estrogen dominance, the saliva becomes more profuse, watery, and elongatable. During the post-ovulatory phase, the saliva becomes less abundant, more viscous and less elongatable.
In healthy women with normal menstrual cycles, ovulation usually occurs between the 12th and 14th day prior to the next menstrual period. Specifically, the saliva is most hydrated (more than 99% watery) at the time of ovulation and is relatively dehydrated (96%-97% watery) at other times. The solid residue present after desiccation may range from 1% during ovulation to 3-4% at other times. With regards to determining time of ovulation on the basis of hormonal changes in the blood or chemical changes in the saliva, present procedures for such analysis have limited use because the results of the precise analysis are not normally available until the cycle advances. These procedures are lengthy and costly and are only adopted for unique situations.
Ovulation is defined as the moment when an ovum is released from the follicle. This knowledge led to the inventor's previous development of techniques for monitoring viscoelasticity, and other properties of saliva, as a predictor of the time of ovulation and to improvements in rheometer or viscometer apparatus for measuring viscoelastic properties (e.g., U.S. Pat. No. 4,002,056). There is a three-to-five day period at the end of which there is a distinct identifiable minimum viscoelasticity and, following ovulation, a one-to-two day period where the minimum viscoelasticity disappears.
A process for measuring the viscoelasticity of sublingual saliva is known. One device has a shape somewhat like a syringe with an outer cup, an inner cup concentric with and located within an outer cup, and a plunger. A plate attached to the end of the plunger holds a saliva sample. The plunger is inserted into the inner cup until the saliva sample is compressed against the plate in the inner cup. A predetermined amount of weight pulls the inner cup downward, stretching the saliva sample. If the viscoelasticity of the saliva is low, the saliva sample will elongate appreciably. If, the viscoelasticity of saliva is high, the saliva sample will hold the plunger and the inner cup nearly together so that the lower cup will not elongate the saliva sample indicating that ovulation will not take place in the near future.
The aforementioned viscoelasticity device is subject to flaws in that a user can improperly calibrate the device and receive an inaccurate reading. The device is also subject to sample contamination. There continues to be a need for an over-the-counter medical device that can provide females with a quick and reliable test for ovulation. Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.